It doesn't matter if GSP weighed in at 170.0 or 170.9, nobody cares for that. The fact that the commission relaxed the rules is the issue here.
Why is that an issue? Commissions are the bodies that set the rules for their jurisdictions. They can make the rules as they see fit, and the fight producers that want to put on fights in those jurisdictions can either abide by those rules, make a request for the commission to apply exceptions to those rules (which the commission can accept or refuse,) or decide not to hold the fights in that jurisdiction.
Commissions can have different rules ... and weight classes vary all over the world http://en.wikipedia.org/wiki/Mixed_m...weight_classes
The rules weren't 'relaxed', they were what they have been for a while now .. check out a few weigh in videos for fights held in Montreal, and you will see that they haven't mentioned a non 'right on the lbs mark" weight for a while now .... the rules are different than some other jurisdictions, but that's nothing new. Why is it 'an issue' just because the rules are not the same as "Americans think they should be
Here for example is a condensed 6 minute video of the weigh ins for UFC 113, held in Montreal (UFC 158, 154, and 166 have been held in Montreal since then) and unless not a single fighter was a single 0.1 lbs over or under an rounded number, then obviously Montreal has had this rule in place for a while now. (And it certainly wasn't to give GSP any advantage as he wasn't even on the card for this event.)
I find it hard to believe that in at least 4 events, with about 100 fighters being weighed in, that not a single one of them looked down to see that their weight was being rounded off and bothered to check it out... how is that possible?
If Diaz went to Japan to challenge for a WW championship weighing 170lbs, and suddenly found that he was no longer a WW, but actually 2 lbs overweight for the MW class, and was now fighting the LHW Champ who weighted the maximum for LHW at 183 lbs, would he be complaining that the champ should have to vacate his belt just because Diaz didn't know the rules in the jurisdiction he was fighting?